The manufacture of semiconductor wafers to create semiconductor integrated circuit devices typically involves a sequence of processing steps which fabricate the multi-layer structure generally associated with the integrated circuit devices. Such processing steps may include (1) the deposition of metals, dielectrics, and semiconductor films, (2) the creation of masks by lithography techniques, (3) the doping of semiconductor layers by diffusion or implantation, (4) the polishing of outer layers (e.g. chemical-mechanical polishing), and (5) the etching of layers for selective or blanket material removal.
There is a continuing trend in the semiconductor industry to increase the functionality and performance of integrated circuit devices by increasing the number of circuit components within a given integrated circuit device. While in certain cases this may be accomplished by increasing the size of the integrated circuit device, in most cases this is accomplished by reducing the size and increasing the density of the circuit components.
Numerous manufacturing techniques have heretofore been developed in an effort to accomplish such component size reductions and density increases. For example, dry etch processes have been developed which do not require the immersion of the semiconductor wafer into an etching liquid. The most common dry etch process, generally referred to as "plasma etching", utilizes plasma to etch films on the semiconductor wafer. Another type of dry etching, generally referred to as "dry developing", utilizes a reactant gas to etch resist films from the semiconductor wafer.
In such dry etch processes, it is generally desirable to predict or detect when the desired layer of material associated with the semiconductor wafer has been etched away. In particular, it is desirable to detect when the semiconductor wafer has been etched to a desired level or "endpoint". For example, systems have heretofore been designed which monitor the emission spectra of the plasma during plasma etching. However, such systems are typically complex and require expensive analysis equipment for operation thereof.
Thus, a continuing need exists for an apparatus and method which accurately and efficiently detects when an etching system etches a semiconductor wafer down to a desired level.